Apparatus for bulk curing tobacco



May 26, 1964 R. w. WILSON APPARATUS FOR BULK CURING'TOBACCO '5Sheets-Sheet 1 Original Filed Sept. 22, 1961 INVENTOR 120mm W. WngonATTORNEYS May 26, 1 R. w. WILSON APPARATUS FOR BULK CURING TOBACCOOriginal Filed Sept. 22, 1961 5 Sheets-Sheet 2 [20mm W. M5014 BYMM; @Z;W

ATTORNEYS May 26, 1964 R. w. WILSON APPARATUS FOR BULK CURING TOBACCOOriginal Filed Sept. 22, 1961 5 Sheets-Sheet 4 FIG. 9

INVENTOR 200221 W. Wn 0u ATTORNEYS May 26, 1964 R. w. WILSON APPARATUSFOR BULK CURING TOBACCO Original Filed Sept. 22, 1961,

5 Sheets-Sheet 5 INVENTOR P0155121 W. Wagon --&v

ATTORNEYS United States Patent s 134 583 APPARATUS non iiurir cUniNGronacco Robert W. Wilson, Charlotte, NC, assignor to R. H.

Bouligny, Ind, Charlotte, N.C., a corporation 0t North Carolina Thisinvention relates to the harvesting and curing of tobacco leaves andmore particularly to improved apparatus for handling and .curing tobaccoleaves. cation is a division of my co-pending application Serial No.140,026, filed September 22, 1961, which issued April 2, 1963, as PatentNo. 3,083,517.

At the present time, tobacco of the bright leaf or flue cured type ishandled to a large extent manually during the harvesting and curingoperations. Bright leaf tobacco must be harvested at a particular timein the growing season and the leaves of the plant ripen at differenttimes, the leaves progressively ripening from the bottom to the top onthe stalk. The conventional practice is for primers to proceed throughthe field three or four times, and in each succeeding pass through thefield the lowermost ripened leaves of the plants are removed by hand bythe primer.

There have been proposals for replacing the conventional manualharvesting procedure with mechanisms capable of removing the ripe leavesfrom the plants by a mechanical action. Examples of mechanisms utilizedfor this purpose are found in Wilson Patents 2,816,411 and 2,834,173 andWilson et al. Patent 2,834,174.

At present, mechanized harvesting of tobacco leaves has not beencommercially adopted largely for the reason that no satisfactory systemof mechanically handling the leaves thus harvested had been available.Conventionally, the primed leaves are handled manually by first placingthem in bunches with their stems commonly aligned and tying thesebunches, called hands, by string or other instrumentality on elongatedtobacco sticks. These sticks were then raised into supporting relationwithin a tobacco barn for curing in the conventional manner.

In recent years there has been proposed a system of handling tobaccoleaves in substantial bulk form by the use of pronged racks. Examples ofracks utilized for this purpose are disclosed in Wilson co-pendingapplication Serial No. 116,368, filed June 12, 1961. A rack of the typedisclosed in the above application is capable of handling approximately130 pounds of leaves or the same quantity of leaves that were previouslyhandled on approximately 8 to 13 tobacco sticks.

In conjunction with the use of these bulk handling racks curing of theleaves must be carried out in the presence of a forced circulation ofheat and air, due to the great quantity of leaves per unit of volumewithin the barn.

The development of this system of handling and curing tobacco leaves inbulk form makes it commercially feasible for the first time to provide atrue tobacco leaf harvesting mechanism capable not only of removing theleaves from the plants but of subsequently handling the mechanicallyharvested leaves so that they are in a condition to be moved directlyinto the curing barn without the necessity of further manual handling.The present application contemplates a true tobacco harvesting machinewhich might be more accurately termed a combine, which is capable duringmovement through a tobacco field of mechanically removing the ripenedleaves from the tobacco plants, conveying the removed leaves to a balingstation where they are loaded in bulk form into and secured within Thisappli' bulk curing racks, and of handling a plurality of the filledracks so that they are retained in a position to be bodily moved into anexisting curing barn and/ or can be utilized to form a part of suchbarn.

An overall study of the entire operation of a tobacco farmer in gettinghis tobacco to the market place has shown that over a period of lessthan approximately 20 years, the man hours required to accomplish theoverall operation including producing the plants, preparing land,transplanting, cultivating, controlling suckers and topping, harvestingand barning, curing, and marketing, has increased from approximately 408man hours to approximately 426 man hours. The greatest increase in anyone of the above-mentioned operations occurs in the harvesting andbarning operation. The above figures are based upon the average manhours required to produce an acre of flue cured tobacco and the increasein man hours required in the harvesting and barning operation can beattributed primarily to the substantial increase in the amount oftobacco leaves that can be produced in an acre as compared withapproximately 20 years ago. Indeed the man hours required in many of theoperations have been reduced, particularly those dealing with thepreparation of the land, cultivating and curing.

It is evident that with the increased cost of labor and the increaseddifliculties in obtaining the necessary labor at the critical times whenit is required, indicate that a commercial apparatus capable ofsubstantially reducing the man hours required in the harvesting andbarning operation constitutes an acute need to tobacco farmers, a needwhich has existed for a considerable period of time. Indeed,conventional practices seem to indicate a resistance on the part oftobacco farmers to adopt mechanized procedures in those operations whichhave been commercially mechanized because of the preference to providework for those laborers which are required during the harvesting season.

The present'invention is more particularly concerned with novelimprovements in the curing operation itself by making a more eflicientuse of a primary heating and air circulating source. In a normal curingoperation the first step involves a chemical reaction within the leaveswherein they change to a yellow color. Very little movement of air and arelatively low temperature in the range of between IOU- F. is requiredduring this stage in the curing procedure. After the chemical reactionhas taken place to a suficient degree, the leaves are then dried by theapplication of considerably higher temperatures and a greater forcedcirculation of air. A typical drying temperature would be between -175F. Thus, in any bulk curing operation there must be provided a source ofcirculating hot air capable of delivering the maximum required for thedrying operation.

Accordingly, it is an object of the present invention to provide atobacco curing barn apparatus capable of achieving the advantages setforth above.

Still another object of the present invention is the provision oftobacco curing barn apparatus which is capable of supporting amultiplicity of tobacco leaves in bulk form and of circulating a currentof hot air therethrough in such a way as to obtain maximum efficiencyfrom the heat source utilized to heat the circulating air.

Still nother object of the present invention is the provision of atobacco curing barn apparatus having means for circulating the productsof combustion of the heating source with the air heated by the source soas to reduce the heat losses to a minimum.

Another object of the present invention is the provision of a devicewhich is capable of being dis-associated from the central heating andair circulating source and utilized in cooperation with the harvestingapparatus so become more apparent during the course of the fol-- lowingdetailed description and appended claims.

The invention may best be understood with reference to the accompanyingdrawings wherein an illustrative embodiment is shown.

' In the drawings:

FIGURE 1 is a perspective view of a rack constructed in accordance withthe present invention, showing the rack sections exploded in theposition in which they are loaded and secured together;

FIGUURE 2 is a perspective view of the rack showing the rack sectionssecured together in the position in which they are handled and supportedwith the curing barn;

FIGURE 3 is a plan view of a curing barn embodying the principles of thepresent invention;

FIGURE 4 is an elevational view of the curing barn shown in FIGURE 3;

FIGURE 5 is an enlarged sectional view taken along the line 5-5 ofFIGURE 4;

FIGURE 6 is an enlarged sectional view taken along the line 66 of FIGURE4;

FIGURE 7 is an enlarged sectional view taken along the line 7-7 ofFIGURE 3;

FIGURE 8 is an enlarged sectional view taken along the line 8--3 ofFIGURE 5;

. racks secured together to form a portion of a curing barn section.

Referring now more particularly to the drawings, there is shown inFIGURES 1 through 9 thereof an apparatus for bulk curing tobacco leaveswhich, as shown, includes a plurality of bulk curing racks, generallyindicated at 16, a plurality of rack supporting devices, generallyindicated at 28, and a fixed curing barn housing section, generallyindicated at 5%.

Each rack 16 and rack supporting device 28 is particularly suited foruse in conjunction with apparatus for mechanically defoliating tobaccoleaves and mechanically handling the defoliated leaves in bulk form.disclosed in Patent Number 3,083,517. In general, the apparatus of thepatent comprises a vehicle frame which is preferably of theself-propelled type capable of movement through a field of maturetobacco. The vehicle frame provides a lower defoliating station at whichthe leaves of the plants are removed during the movement of the vehicleframe through the field, an upper forwardly positioned leaf balingstation at which the removed leaves are secured within the bulk curingracks 16, and an upper rearwardly positioned rack handling station atwhich the loaded racks are handled for purposes of storage andfacilitation of their subsequent transportation to a remote curingstation for curing of the tobacco supported therein.

The preferred apparatus includes a defoliating mechanism carriedby thevehicle frame at the defoliating station thereof for vertical movementwith respect to the vehicle frame into different positions of verticaladjustment depending upon the position of the leaves to be defoliated onthe tobacco stalks within the field. Mounted for vertical movement withthe defoliating mechanism is is positioned on the vehicle frame at therack handling station thereof for effecting movement of the racks loadedby the rack loading and securing mechanism away from i the latter into arack supporting device 28 which is preferably constructed so as toreceive and support a plurality of loaded racks so that the loaded rackssupported therein can be conveniently transported from the vehicle frameto the curing station. The present apparatus also provides an elevatingmechanism for handling successive rack supporting devices 28tofacilitate their transportation to the curing station.

Rack

As best shown in FIGURES 1 and 2, each rack 16 utilized in connectionwith the present apparatus is preferably of the type disclosedinco-pending Wilson application Serial No. 116,368 which is'herebyincorporated by reference into this disclosure. While the rack shown inthe present drawingsembodies the principles of the construction of therack disclosed in the above-mentioned co-pending application, it isparticularly dimensioned to cooperate with the rack loading and securingmechanism of the apparatus disclosed in Patent Number 3,083,517. To thisend, each rack 16 includes a pair of cooperating sections 312 and 314which are moved apart to permit leaves to be loaded therein and aremoved into cooperating latched relationship to secure the loaded leavesin baled condition. In secured relation, the bale provides peripheralconfinement to the leaves in bulk form loaded therein. Thus, the section312 includes a U-shaped frame, the legs of which are formed by angularmembers 316 and 313. These leg members are interconnected by a pair oftransversely extending angle iron frame members 326 and 322.

As best shown in FIGURES 1 and 2 the ends of the angle iron frame member322 are rigidly secured, as by welding or the like, in abutting relationto the lower corners of the vertical flanges of the angular leg members316 and 318. In a like manner, the ends of the angle iron member 320 aresecured, as by welding or the like, to the adjacent outwardly extendingflanges of the angle iron leg members 316 and 318. Rigidly secured tothe inwardly extending flanges of the angle iron frame members 32d) and322 is a plurality of prongs or elongated rods 324. The prongs 324 arespaced apart approximately 3%. inches with the prongs secured totheangleiron member 320 spaced intermediate the prongs of the angle ironmember 322. Preferably, these prongs extend at a slight angle withrespect to the plane of the associated flanges so as to permitdeflection of their outer ends in supporting relation to the othersection 314 of the rack. Preferably, the outer ends of the prongs aresharpened to a blunt point to facilitate their penetration through theleaves.

Each of the leg members 316 and 318 is provided at the end thereofopposite from the angle iron members 329 and 322 with a pair of guidespaced plates 326 arranged to guidingly cooperate with the outwardlyextending ends of a pair of angle iron frame members 328 and 330 forminga portion of the rack section 314. The angle iron members 328 and 330 ofthe section 314 are rigidly interconnected in spaced relation by endframe members 332 to which are secured spring latch members 334 arrangedto cooperate with spring latch members 336 adjustably secured to the legmembers 316 and 318 of the section 32. It will be seen that when the twosections are moved together the cooperating latch members will hold thesections in interengaged secured relation with respect to each other. Itwill also be noted that an apertured handling lug or inverted U-shapedrod 338 is fixedly secured to the central portion of the outwardlyextending flange of each leg member 316 and 318.

Rack Supporting Device The rack supporting device 28 is best shown inFIG- URE 3 and comprises a pair of side walls 474 which are preferablyconstructed of laminated panels, as for example, inner and outer panelsof masonite having suitable insulating material therebetween. The sideWalls are connected along their lower edges by spaced floor slats 476which serve to retain the lower portions of the side walls in rigidspaced relation. The upper ends of the side walls are connected by apitched roof 4'7 8 which is likewise preferably made of heat insulatedlaminated panels. Mounted on the interior surface of each of the sidewalls 474 is a pair of vertically spaced horizontally extending angleirons 480 which serve as rail means to engage and support the outwardlyextending flanges of the leg members 316 and 318 of the rack sections312. As shown, the device 28 is open at both ends and the side walls 474are of such a dimension as to receive approximately five abutting racks16 mounted on the rails 480 extending therethrough. Since there are twocooperating rails provided at two different vertical levels, the entiredevice 2% as shown, is capable of receiving ten loaded racks.

Preferably, the lower edge surface of the side walls are provided withlongitudinally extending runners 482 to aid in handling the device. Therack supporting device 28 is thus adapted to engage on the upper surfaceof the U-shaped frame of the elevating mechanism and when the latter isdisposed in its upper position, one open end of the container will bedisposed in a position facing the rack handling station on the vehicleframe.

Curing Barn As best shown in FIGURES 3-9, the curing barn of the presentinvention preferably comprises a fixed housing section, generallyindicated at 500, arranged to cooperate with a plurality of racksupporting devices 28. As best shown in FIGURE 6, the fixed housingsection 500 includes a rectangular foundation wall 502 which may beconveniently constructed of cinder block or the like, suitably mountedon concrete footings formed in the ground, the ground itself providing abottom floor, indicated at 504, for the housing section 500. Mounted onthe upper surface of the foundation wall 502 is a lower intermediatefloor 506 of any conventional construction. Extended upwardly from thefoundation wall in surrounding relation to the floor 506 is a pair ofparallel side walls 508 interconnected at their endsby a pair of endswalls 510. These walls may also be of any suitable construction andpreferably they are made. up of individual laminated panels, each panelof which comprises a pair of spaced outer sheets of wall material suchas masonite or the like, having suitable insulating material, such asfiberglass or the like, disposed therebetween in a manner similar to thepanels of the device 28.

The upper edges of the side and end walls are interconnected and coveredby a conventional roof construction indicated at 512. While the roof isshown in FIGURES 3, 8 and 9 as being pitched, it will be understood thatit may be horizontal and any desired pitch angle may be provided thereonfor purposes of drainage and the like. Mounted in vertically spacedrelation to the roof 512 is an upper intermediate floor 514 of anysuitable construction. Preferably, one of the end walls 510 is providedwith a louvred door 516 as shown in FIGURE 4, which permits fresh air toenter the central portion of the housing section between theintermediate walls 506 and 514.

Disposed in the central portion of the housing section 500 betweenthe'floors 506 and 514 is a furnace assembly unit 518 which constitutesa source of heated circulating air. As best shown in FIGURES 8 and 9,the furnace unit 518 comprises a rectangular casing or housing 520 whichpreferably includes front and rear housing walls 522, side walls 524 andbottom and top walls 526 and 528 respectively, all of the walls being ofsheet metal construction and secured to the exterior of a suitableskeletonized frame. Formed in the top wall 528 is a rectangular inletopening 530 to which is secured a duct structure comprising a pair oftrapezoidal shaped end walls 532 having the lower ends thereof securedadjacent the ends of the inlet opening 530 in the top Wall 528 and theirupper ends disposed adjacent a smaller inlet opening 534 formed in theupper intermediate floor 514 of the housing section 500. Extendingbetween the inclined upright edges of each of the trapezoidal end walls532 is a damper plate 536 which is pivoted at its upper end about ahorizontal axis for movement into different positions of adjustment withrespect to the associated opening which constitutes a fresh air inletfor the furnace unit.

Mounted in the upper central portion of the housing 521) and extendingbetween the front and rear walls 522 thereof is a fixed deflector orbaffle plate 538 which is of concavo-convex arcuate configuration withthe concave side thereof facing downwardly. Disposed beneath the bafileplate 538 is a cylindrical burner casing 540 closed at its rear end andformed along its upper portion with an elongated rectangular combustiongas outlet opening 542 disposed in vertically spaced relationshipbeneath the baffle plate 538. The portion of the housing front wall 522enclosing the front end of the burner casing is provided with acentralcircular opening 544 within which a burner assembly 546 may beintroduced into the burner casing and maintained therein so that thecontrols thereof extend outwardly of the front wall of the main housing.The opening 544 also provides an inlet through which air to supportcombustion may enter the burner casing 540. The burner assembly 546 maybe of any conventional construction capable of burning either gas, oil,kerosene, or other conventional fuels.

Mounted within the lower central portion of the housing 520 is a fancasing 548 which includes an outer volute peripheral wall 556 having oneend secured to the bottom wall 526 of the housing adjacent one end of anoutlet opening 552 formed therein and extending therefrom upwardlyaround and then downwardly to the opposite end of the opening 552. Thesides of the volute peripheral wall 550 are enclosed by side walls 554,each of which has an inwardly extending circular opening 556 formedtherein. Mounted between the side walls 524 of the housing 520 andextending through the axis of the openings 556 is a shaft 558 having afan r'otor 560 fixed thereto within the casing 548 between the sidewalls 554. The fan rotor 56% is of conventional construction preferablyof the type adapted to receive air axially through the axial openings556 and convey the same radially outwardly through the outlet opening552. It will be noted that the shaft 558 extends outwardly through onehousing side wall 524 and is driven by a variable speed electric motor562, or other suitable means, such as an internal combustion engine,through a suitable belt and pulley assembly 564.

Referring now more particularly to FIGURE 5, it will be noted that thespace within the housing section 500 defined by the roof 512 and theupper intermediate floor 514 defines an inlet chamber 566 and theassociated portion of each side wall 508 is provided with a pair ofhorizontally spaced openings 568 positioned to communicate with the openupper end portion of a rack supporting device 28. Each of the openings568 is provided with a horizontally pivoted damper plate 570 forcontrolling the communication of the associated opening 568 with theinlet opening 534 in the floor 514.

As best shown in FIGURE 6, the ground floor 502 and lower intermediatefioor 506, define an outlet chamber 572 which communicates through thelower intermediate floor 506 with the outlet opening 552 of the fancasing 548. Each side of the foundation Wall 502 is provided with a pairof horizontally spaced rectangular openings 574 disposed verticallybelow the associated pair of openings 568, each being controlled by ahorizontally pivoted damper plate 576.

The above described structure constitutes the main sourceof heatedcirculating air which is of suitable capacityto accomplish the moredemanding procedure of drying the tobacco leaves. The present curingbarn also includes a separate circuit for separately accomplishing theyellowing procedure which does not require high heat shown in FIGURE 5.The pair of openings 578 adjacent each end wall 510 is intercommunicatedby a triangular duct section 582 and the duct sections 582 areintercommunicated by a longitudinally extending duct section 584.

A round vertical duct section 536 has its upper end communicativelyconnected with the longitudinal duct section 584 and extends downwardlythrough the intermediate floors 514 and 506 and has its lower endcommunicatively connected intermediate the ends of a longitudinallyextending duct section 588 disposed within the outlet chamber 572. Theends of the duct section 588 are communicatively connected intermediatethe ends of a pair of duct sections 590, each of which has the endsthereof communicating with openings 592 formed in the foundation Wallsadjacent the outer ends of the associate pair of openings 574. Asbefore, a horizontally pivoted damper plate 594 is mounted in eachopening 592 to control the flow of air therethrough.

Mounted in the vertical duct section 586 is a suitable forced airsource, such as a fan which may be conveniently driven by the motor 562through an appropriate belt and pulley assembly 598 connected with thefan shaft through a right angle drive assembly 6% or the like.

Preferably, the belt and pulley assembly 5% is such that it may beconveniently disconnected or otherwise clutched to control the drive tothe fan 596. The vertical duct foundation walls 666 are disposed so asto receive the runners 4% on the side walls 474 of a rack supportingdevice 28, so that the roof 4'78 of the device will cover the associatedupper openings 56% and 5'78 in the housing section side walls 538.

As can be seen from FIGURES 3 and 4, the foundation walls 6% are suchthat they will support in aligned condition a plurality of the devices28 disposed in end-to-end V abutting relation. Rather than utilizing theedge wall constructions of the device as an abutting means in the mannershown, the edges of the devices may be provided with suitable sealingmeans (not shown) so as to efiect a substantial sealing engagementbetween the same and with the associated side wall of the fixed housingsection Silt). In this way, each of the devices 28 defines a housingsection of the curing barn. When a sufiicient number of devices has beenplaced in end-to-end relation, the outer end of the outermost device isclosed by a back plate or panel 610. The back panel 6M9 is provided witha pair of horizontally spaced chain engaging crank fittings 612, each ofwhich is arrangedto engage one end portion of a chain 614, the oppositeend of which issecured to the fixed housing section Silt). It will beseen that by actuating the crank fittings 612, the back panel 610 andall of the aligned devices 28 will be moved into substantial sealingengagement with respect to each other and with respect to the associatedside wall 508 of the housing section Silt).

devices 2% passes vertically upwardly through the tobacco leaves mountedwithin each and the upper surfaces of the tobacco leaves define with theroofs 478 of the devices an upper duct which is controllably closed atone end by the back panel 610 and communicates at its other end with theassociated openings 568 and 578 in the housing sec? tion 5% under thecontrol of the associated dampers 570 and 589. Thus, the air in theupper duct is returned to the inlet chamber 566 for recirculationthroughthe furnace assembly 518.

For the purpose of controllably closing one end of the upper ductprovided by the devices 28, each back panel 61% is provided with alouvre assembly 616. As shown in FIGURE 9, the louvreassernbly 616 is ofthe type which is normally biased into a closed position and which isopenable in one direction only. Thus the louvres are adapted toautomatically open when a predetermined pressure is built up in theupper duct of the devices 28 to permit outward movement of airtherethrough but will also prevent movement of outside air into theupper duct.

Curing Barn Operation and Curing Method The curing barn is such that thefurnace assembly 513 is capable of accomplishing the entire curingoperation. It will be noted that the furnace assembly 518 efiiciently.utilizes the heat input by discharging all of the products ofcombustion into the circulated air through the opening 542 of the burnercasing 540. When it is desired to utilize the furnace assembly 513 toaccomplish the yellowing procedure of the curing'operation, the speed ofthe fan rotor 560 may be adjusted, if necessary, by adjusting the speedof the motor 562, to obtain a relatively slow flow of air and thethermostat (not shown) controllingthe burner assembly 54-6 is turneddown within a temperature range of approximately to F. Of course, whenthe furnace assembly 518 is used in this way, the drive to the fan 5% isdisconnected and all of the dampers 580 and 594 associated with theyellowing circuit are closed. During the yellowing procedure, thecirculated air is heavily laden with moisture and this moisture can beexpelled by opening the fresh air dampers 536. In this way, a

greater pressure is created in the associated upperduct of the device'28and the louvre assembly 616 will open to permit exhaust of the humidair.

In the operation of the furnace assembly 518 in its normal use duringthe drying procedure, the speed of the fan 568) may be adjusted, ifnecessary, to give a'flow of air of approximately 30 cubic feet perminute and the thermostat for the burner is set to operate at atemperature range of to F. Here again, the moisture in the circulatedair can be controlled by opening the fresh air dampers 536.

Bulk tobacco curing of the present type, as distin guished from curingof tobacco hands tied on sticks, de- A pends upon air pressure to obtaincirculation. It is for this reason that the essentials indicated aboverelating to the manner in which the leaves are compressed into the racksare required. That is, the leaves must be aligned generally in onedirection to provide vertical flow paths for the air under pressure.Moreover, there-must be general uniformity in the density of the leavescompressed within all of the racks in order to insure that air will flowthrough all of the vertical paths provided. That is, if one or two racksare loosely loaded while one or two other racks in the same room sectionare tightly loaded, the air will tend to follow the path of leastresistance and substantially no flow willpass through the tightly loadedleaves. Also for this reason the racks themselves must be placed in theroom section so that there are no open vertical passages provided whichwould divert the flow of air from passing between the paths providedbetween the leaves. This means that the racks must be supported at theirends so that they are substantially sealed with respect to the walls ofthe room section supporting the same, as by the supporting rails, thatthe sides of adjacent racks must be substantially sealed, as by abuttingengagement or suitable resilient seals, not shown, and that the innerand outer sides of the innermost and outermost racks must besubstantially sealed with respect to the adjacent side wall of centralhousing section and the back panel respectively, as by abuttingengagement or suitable resilient seals, not shown.

In regard to the rate of air flow, it should be noted that the rate ofair flow during the yellowing procedure and the rate of flow during thedrying procedure will not normally be in direct relation to the speed ofthe fan 56%. Bearing in mind that a green newly defoliated leaf is from6 to 8 times the size of a cured leaf, it can be readily seen that thegreen leaves during the yellowing step will olfer considerably moreresistance to flow than the same leaves during the drying step. Thischange in size is mostly in the thickness of the leaves as a result ofloss of moisture and therefore the flow paths between the leaves willtend to open more and more as the curing progresses.- Thus, it ispossible to utilize a constant speed for the fan and the variations inthe flow required for the yellowing and drying steps will be providedmore or less automatically on the average as a result of the lesseningof resistance to flow due to leaf shrinkage.

While the furnace assembly 518 may be utilized without the yellowingcircuit to accomplish the entire curing operation, the present inventioncontemplates the utilization of the yellowing circuit in an improvedmethod whereby the more expensive furnace assembly 518 is utilized tothe greatest possible efficiency, namely, to accomplish the dryingprocedure while the yellowing circuit is simultaneously employed toaccomplish the yellowing procedure. It will be noted that the ductsystem of the yellowing circuit is disposed within the inlet and outletchambers 566 and 572 in heat exchange relation to the air therein whichshould provide sufiicient temperature to the yellowing circuit air inthe range of 100 to 110 F. Moreover, a relatively inexpensive fan unit596 will provide the necessary relatively slow air flow required. Withrespect to the maintenance of the air of the yellowing circuit at theproper temperature, it will be noted that the majority of the yellowingcircuit is in heat exchange relation to the main circuit within theupper and lower chambers which are insulated from ambient conditions andmaintained at a relatively constant operating temperature. Therefore,the heat transfer characteristics are generally constant. However,variations will be introduced when the temperature of the ambient airintake varies. In order to eliminate the need for continued manualadjustment of the damperplate 604, an automatic adjustment mechanism(not shown) operable to open and close the damper 604 in response tovariations in the air temperature within the yellowing circuit can beprovided.

A specific illustrative embodiment of the present method will now bedescribed in relation to FIGURES 3 and 4 wherein the separate groups ofdevices 28 are designated by the reference characters A, B, C and D.Bearing in mind that the total harvesting procedure requiresapproximately four or five passes through the tobacco field wherein thelower, intermediate and upper leaves of the 1t stalks are defoliatedrespectively, and that the period between such passes is approximatelyone week, the following schedule specifically exemplifies the principlesof the present method, wherein the days of the week are arbitrarilychosen and designated with consecutive numbers for the sakeofconvenience.

On Monday 1, sections A and B are loaded. On Tuesday 2, the furnaceassembly 518 is utilized in the manner described above to provide arelatively low heat, low flow circulation through sections A and B tobegin the yellowing process of the tobacco in sections A and B. OnWednesday 3, the yellowing of the tobacco in sections A and B iscontinued. On Thursday 4, the dampers 5'70 and 576 to sections A and Bare adjusted to provide a relatively high temperature, high flow aircirculation to commence the drying process and during the same daysections C and D are loaded. On Friday 5, the drying of the tobaccoleaves in sections A and B is continued and the dampers 580 and 592associated with sections C and D are opened and the fan 596 is drivinglyconnected so as to provide a low heat, low flow air circulation throughthe tobacco therein to commence the yellowing process. On Saturday 6 thedrying of the tobacco in sections A and B is continued and completed,and the yellowing of the tobacco in sections C and D is continued. OnSunday 7 the yellowing circuit is closed down and the dampers 570 and576 associated with sections C and D are adjusted to commence the dryingprocess therein while sections A and B remain closed from aircirculation.

On Monday 8, sections A and B are unloaded and reloaded and the dryingprocess in sections C and D is continued. On Tuesday 9, the dampers 580and 594 in sections A and B are adjusted to begin the yellowing processwhile the drying process is continued in sections C and D and completed.On Wednesday 10 the yellowing of the tobacco in sections A and B iscontinued with the use of the furnace unit 513 and sections C and D areunloaded with the yellowing circuit closed. On Thursday ll, the dampers570 and 576 associated with sections A and B are adjusted to begin thedrying process and sections C and D are loaded. On Friday 12 the dryingprocess is continued in sections A and B and the dampers 580 and 594associated with sections C and D are adjusted to begin the yellowingprocess. On Saturday 13 the drying of the tobacco in sections A and B iscontinued and completed and the yellowing of the tobacco in sections Cand D is continued and completed. On Sunday 14, the dampers 579 and 576associated with sections A and B remain closed along with the yellowingcircuit, while the dampers 570 and 576 associated with sections C and Dare adjusted to begin the drying process. On Monday 15, sections A and Bare unloaded and re-loaded and the drying process is continued insections C and D. On Tuesday 16, the yellowing of the tobacco insections A and B is begun with the yellowing circuit and the drying ofthe tobacco in sections C and D is continued and completed.

The above schedule gives a clear indication of a continuous cycle of useof a central heated circulating air source, such as provided by thefurnace assembly 418, in which the source is utilized most efiicientlywhile at the same time providing for a minimum labor on Sunday or oneday out of seven.

Modifications struction generally indicated at 664. As shown, the rack664 includes four separable sections, a pair of end wall sections 666, aprong section 668, and a side closure section 670. Each end wall section666 is preferably of position. 668 with the end wall sections 666latched thereto is rectangular configuration and is made up of a pair ofspaced outer plate members having a suitable insulating materialdisposed therebetween. The vertical dimension of the end wall section isof a size generally greater than the vertical dimension of the leavessupported in the rack 664 in the size range of between 28 to 32 inches,a preferablydimension being 30 inches.

Each edge of each end wall section 666 is provided with means forsubstantially 'sealingly engaging the opposite edge of a similar rack.To this end, it will be noted tending ridge 672 therein, while the loweredge is formed with a mating groove 674 therein. in like manner, one

' vertical edge of each side wall section 666 is provided with anelongated ridge 676, while the other is provided with a cooperatingvertically extending groove 6'78.

Mounted on the interior surface of each end wall'section 666 is ahorizontally extending spring clip 680 having opposite ends thereofprovided with hooked portions 682 disposed in a position spaced justinwardly from the adjacent vertical edge thereof.

The prong rack section 663 includes an elongated member 634 preferablyof channel construction having a pair of horizontally spaced rows ofprongs 636 fixedly secured, as by welding or the like, to the upper andlower flanges thereof, the prongs of one row being staggered withrespect to the prongs of the other row. Mounted on each of the members684 is a latch clip 688 arranged to cooperatively engage within anassociated hooked end portion 632 of the end wall section spring clips6%. The side closure rack section 6'70 comprises an elongated member 6%preferably of channel construction having a latch clip 692 mounted oneach end thereof for cooperation with the other hooked end porticns 682of the spring clips 68%.

- relation with respect to the end wall sections 666. To

this end, the interior surface of the end wall sections 666 arepreferably provided with two pairs of vertically spaced guide plates 693defining inwardly converging surfaces for guiding the associated end ofthe rack section members 684 and 6% into proper latched relation and forpreventing relative vertical movement when in latched It will be seenthat the prong rack section comparable to the rack section 312previously described while the side closure section 670 is comparable tothe section 312 previously described.

Accordingly, the rack 664- may be utilized in this way in lieu of therack 16 previously described. Moreover, with the rack 664 it is possibleto initially assemble the side closure section 676 with the end wallsections 666 in latched relation. When the rack 66% is thus utilized,the rack section receiving and tobacco leaf guide units 342 and 622 neednot provide end walls since the end wall sections 666 serve to confinethe tobacco leaves at the ends.

The sectionalized structure of the rack 664 provides the advantage thatthe various separate sections may "be stored separately thus alleviatingthe storage problem on the vehicle frame of the apparatus of PatentNumber 3,083,517 to a considerable extent. The rack sections may beinitially secured together in themanner indicated above ina simplemanner during the operation of the apparatus of the patent.

It will be noted that the lower edges 674 of the rack end wall sections666 provide a means for supporting the rack on a horizontal surface, theprongs 686 being spaced vertically thereabove a distance suflicient toenable the tobacco leaves to be'supported with their lower surfacesabove such horizontal supporting surface.

Referring now more particularly to FIGURE l1,,it will be noted that aplurality of loaded racks 664 can be with the upper edges 6720f the endwall sections of the lower racks. Any suitable means may be provided forsecuring the racks in stacked relation, as for example cO- operatinglocking elements 694 and 696 of the window latching type mountedadjacent the upper and lower edges on the exterior surface of each endsection 666. In a like manner, a plurality of racks may be mounted inend-to-end abutting relationship in which case the vertical edge 676 ofone rack is disposed in abutting relation to the vertical edge 678 ofthe adjacent rack. Again, any suitable means may be provided forsecuring the racks in end-to-end relation such as cooperating lockingelements 6% and 70d of the window latching type securing to the outersurface of each and adjacent the vertical edges thereof.

As best shown in FIGURE 11, it can be'seen that ten racks 664 mounted intwo vertically stacked rows of five racks disposed in end-to-endrelation form vertical walls of a housing section similar to the sidewalls 474 of the devices 28. In will be understood that a suitableroofconstruction (not shown) may be mounted on the upper edges of the upperracks and that the lower edges of the lower rows of racks may be mountedin cooperating relation to a wall structure defining a lowerducttsection in the manner previously described.

It thus will be seen that the objects of this invention have been fullyand effectively accomplished. It will be realized, however, that theforegoing specific embodiment has been shown and described only for thepurpose of illustrating the principles of this invention and is subjectto extensive change without departure from such principles. Therefore,this invention includes all modifications encompassed within the spiritand scope of the following claims.

I claim:

1. A portable device for supporting defoliated tobacco leaves in bulkform for transportation and curing comprising a pair of uprightimperforate Walls and an imperforate roof extending between the upperportion of said walls, a plurality of racks, rail means on said wallsextending in parallel horizontal relation substantially throughout thelongitudinal extent of said walls for slidably receiving and supportingsaid plurality of racks in side-by-side operative abutting relation,each of said racks including relatively movable sections which togetherprostantial portion of the fiat surfaces thereof in substantiallyparallel vertical relation and spaced horizontal prong means extendingbetween the confining means adapted to be in piercing relation to theleaves in a direction pe1pen' dicular to the parallel flat surfacesthereof so as to provide interior support for the leaves Whilepermitting vertical flow of air between the leaves within the confiningmeans, the rectangular structure of each of said racks including spacedpairs of opposed sides, one pair of opposed sides having downwardlyfacing surface means for slidably engaging said rail means, thelongitudinal extent of said iinperforate walls and the rail meansthereon being related to the longitudinal extent of said one pair ofopposed sides of each rack so that a plurality of said racks aresupported in longitudinal coextensive relation with said walls when theother pair of opposed sides of adjacent racks are in operative abuttingrelation, the upper surface of the leaves supported in said racks beingadapted for defining with said roof an open ended duct permittinghorizontal flow of air therethrough, said walls and roof being of a sizeand weight such as to be conveniently transported through a tobaccofield so that successive racks with newly defoiiated tobacco leavestherein can be mounted on said rail means during such transportationthrough the field, said walls and roof having means at each of the endsthereof for substantiallysealingly abutting the opposite end of asimilar device so that said walls and roof with said plurality of filledracks mounted on said rail means in side-by-side relation coextensivewith said walls is operable to form an exterior portion of a curing barnin which a circulating flow of heated air under pressure suitable tocure the tobacco leaves is established vertically through the leavesconfined by said racks and horizontally through said open ended duct.

2. A device as defined in claim 1 wherein said rail means includes upperand lower pairs of parallel horizontally extending rails.

3. A device for supporting 'defoliated tobacco leaves in bulk form fortransportation and curing comprising a pair of upright imperforate wallsand an imperforate roof extending between the upper portion of saidwalls, means extending between said Walls for supporting a multiplicityof tobacco leaves in bulk form therebetween substantially throughout thelongitudinal extent thereof with the flat surfaces of said leavesextending Vertically and with a substantial portion of the flat surfacesparallel so as to permit vertical air flow therethrough, the uppersurfaces of said leaves being adapted for defining with said roof anopen ended duct permitting horizontal flow of air therethrough, saidwalls and roof having means on each of the ends thereof forsubstantially sealingly abutting the opposite end of a similar device,said walls comprising a plurality of rectangular wall sections securedtogether in vertically stacked and end-to-end relation, said tobaccoleaf supporting means comprising spaced horizontally extending prongmeans directly connected between each pair of spaced corresponding wallsections.

4. A tobacco leaf supporting rack comprising separable rack sectionswhich together in cooperating relation provide means for peripherallyconfining a batch of leaves disposed with their fiat surfaces verticaland with a substantial portion of the flat surfaces thereof insubstantially vertical parallel relation and spaced prong meansextending horizontally within said peripheral confining means in adirection perpendicular to the parallel fiat surfaces thereof so as toprovide interior support for the leaves while permitting vertical fiowof air between the leaves within said confining means, said confiningmeans including imperforate end walls extending generally parallel tosaid prong means, said end walls having a vertical dimension adapted tobe greater than the general vertical dimension of the batch of leavessupported therebetween, each edge of each end wall having means thereonfor substantially sealingly engaging the opposite edge of thecorresponding end wall of a similar rack.

5. A rack as defined in claim 4 wherein securing means is mounted on theexterior surface of each end wall adjacent each edge thereof forlockingly engaging with cooperating securing means on the adjacent endwall edge of a similar rack disposed in substantial sealing engagementtherewith.

6. A tobacco curing barn comprising a fixed housing section defining anair inlet and a vertically spaced air outlet, heating means in saidfixed housing section between said inlet and said outlet, means in saidfixed housing section for creating an air circulation from said inlet tosaid outlet in heat exchange relation to said heating means, anelongated housing section extending horizontally outwardly from saidfixed housing section, said elongated housing section including uper andlower ducts extending longitudinally therethrough, one of said ductscommunicating with said inlet, the other of said ducts communicatingwith said outlet, at least the portion of said elongated housing sectiondisposed above said lower duct comprising a plurality of movable housingunits, each housing unit comprising a pair of upright imperforate wallsand a generally imperforate roof extending between the upper portion ofsaid Walls, means extending between said walls for supporting amultiplicity of tobacco ltd leaves in bulk form therebetweensubstantially throughout the longitudinal extent thereof with the flatsurfaces of said leaves extending generally vertical and a substantialportion thereof parallel so as to permit vertical air flow therethroughand the upper surface of said leaves being adapted for defining withsaid roof a portion of said upper duct permitting horizontal flow of airtherethrough, each of said movable housing units being open at bothends, means for mounting said group of movable housing units insubstantially sealingly abutting end-to-end relation with respect toeach other with one end of the group in substantially sealingly abuttingrelation to said fixed housing section and means for closing the otherend of the group of end-to-end housing units.

7. A device as defined in claim 6 wherein said tobacco supporting meanscomprises a plurality of racks having spaced horizontally extendingprong means for supporting tobacco leaves therein and wherein said wallshave horizontally extending rail means thereon supporting said rackstherebetween.

8. A device as defined in claim 6 wherein said walls comprise aplurality of rectangular wall sections secured together in verticallystacked and end-to-end relation, and wherein said tobacco leafsupporting means comprises spaced horizontally extending prong meansdirectly connected between each pair of spaced corresponding wallsections.

9. A tobacco curing barn comprising a fixed housing section defining anair inlet and a vertically spaced air outlet, heating means in saidfixed housing section between said inlet and said outlet, means in saidfixed housing section for creating an air circulation from said inlet-to said outlet in heat exchange relation to said heating means, anelongated housing section extending horizontally outwardly fromsaidfixed housing section, said elongated housing section includingupper and lower ducts extending longitudinally therethrough, one of saidducts communicating with said outlet, at least the portion of saidelongated housing section disposed above said lower duct comprising aplurality of movable housing units, each housing unit comprising a pairof upright imperiorate walls and a generally imperforate roof extendingbetween the upper portion. of said walls, rail means on said wallsextending in parallel horizontal relation substantially throughout thelongitudinal extent of said walls for slidably receiving and supportinga plurality of racks of the type having means for peripherally confininga batch of leaves disposed with their flat surfaces in substantiallyvertical relation and a substantial portion thereof parallel and spacedhorizontal prong means extend- .ing between the confining means inpiercing relation to said movable housing units being open at both ends,

means for mounting said group of movable housing units in substantiallysealingly abutting end-to-end relation with respect to each other withone end of the group in substantially sealingly abutting relation tosaid fixed housing section and means for closing the other end of thegroup of end-to-end housing units.

10. A tobacco curing barn comprising a fixed housing section defining atleast two separate air inlets and two separate air outlets spacedvertically with respect to said inlets, heating means in said fixedhousing section between said inlets and outlets, means in said fixedhousing section for creating an air circulation from said inlets to saidoutlets in heat exchange relation to said heating means, at least twoelongated housing sections extending horizontally outwardly from saidfixed housing section, each of said elongated housing sections includingupper and lower ducts extending longitudinally 153 therethrough, one ofsaid ducts communicating with one of said inlets, the other of saidducts communicating with one of said outlets, at least the portion ofeach of said elongated housing sections disposed above the associatedlower duct comprising a plurality of movable housing units, each housingunit comprising a pair of upright generally imperforate heat insulatingwalls and a generally imperforate roof extending between the upperportion of said walls, means extending between said walls for suportinga multiplicity of tobacco leaves therebetween substantially throughoutthe longitudinal extent thereof with the fiat surfaces of said leavesextending generally vertical and a substantial portion thereof parallelso as to permit vertical air flow therethrough, the upper surfaces ofthe leaves being adapted for defining with said roof a portion of theupper duct of the associated elongated housing section, each of saidmovable housing units being open at both ends, means for mounting saidgroup of movable housing units in abutting endto-end relation withrespect to each other with one end of the group in abutting relation tosaid fixed housing second and 'meansfor closing the other end of thegroup of end-to-end housing units.

11. A devi e as defined in claim wherein said tobacco supporting meanscomprises a plurality of racks having spaced horizontally extendingprong means for supporting tobacco leaves therein and wherein said wallshave horizontally extending rail means thereon supporting said rackstherebetween.

12. A device as defined in claim 10 wherein said walls comprise aplurality of rectangular wall sections secured together in verticallystacked and end-to-end relation, and wherein said tobacco leafsupporting means comprises spaced horizontally extending prong meansdirectly conected between each pair of spaced corresponding wallsections.

13. A tobacco curing barn comprising a fixed housing section defining atleast two separate air inlets and two separate air outlets spacedvertically with respect to saidv said outlets in heat exchange relationto said heating means, at least two elongated housing sections extendinghorizontally outwardly from said fixed housing section, each of saidelongated housing sections including upper and lower ducts extendinglongitudinally therethrough, one of said ducts communicating with one ofsaid inlets, the other of said ducts communicating with one of saidoutlets, at least the portion of each of said elongated housing sectionsdisposed above the associated lower duct comprising a plurality ofmovable housing units, each housing unit comprising a pair of uprightgenerally imperforate heat insulated walls and a generally imperforateroof extending between the upper portion of said walls, rail means onsaid walls extending in parallel horizontal relation substantiallythroughout the longitudinal extent of said walls for slidably receivingand supporting a plurality of racks of the type having means forperipherally confining a batch of leaves disposed with their flatsurfaces in substantially vertical relation and with a substantialportion thereof parallel and spaced horizontal prong means extendingbetween the confining means in piercing relation to the leaves in adirection perpendicular to the parallel flat surfaces thereof so as toprovide interior support for the leaves while permitting vertical flowof air between the leaves within the confining means, the upper surfacesof the leaves supported in said racks being adapted for defining withsaid roof and open ended duct permitting horizontal flow of airtherethrough, each of said movable housing units being open at bothends, means for mounting said group of movable housing units in abuttingend-to-end relation with respect to each other and with one end of thegroup in abutting relation to said fixed housing section and means forclosing the other end of the group of end-to-end housing units.

14. A tobacco curing barn comprising a fixed housing section defining atleast two pairs, of cooperating vertically spaced inlets and outlets,heating means in said fixed housing section between said inlets andoutlets, means in said fixed housing section for creating an aircirculation from said inlets to said outlets in heat exchange relationto vsaid heating means, means in said fixed housing section forseparately controlling the flow of heated air through each pair ofcooperating inlets, at least two elongated housing sectionsextending'horizontally outwardly from said fixed housing section, eachof said elongated housing sections including a pair of spaced uprightimperforate wall surfaces, a generally imperforate roof extendingbetween the upper portion of said wall surfaces, an imperfo rate floorextending between the lower portion of said wall surfaces, meansextending between said wall surfaces for supporting a multiplicity oftobacco leaves therebetween with the fiat surfaces of said leavesextending generally vertical and with a substantial portion thereofparallel so as to permit vertical airflow therethrough, the

upper surfaces of said leaves being adapted for defining with said roofan upper duct permitting horizontal flow of air therethrough which isclosed at one end against inward flow, the lower surfaces of said leavesdefining with the-floor a lower duct closed at one end, the open end ofthe upper and lower ducts of each elongated housing sectioncommunicating with one pair of said spaced inlets and outlets wherebythe circulation of heated air through each housing section isindependent of the circulation of heated air through the other housingsection so as to permit the simultaneous yellowing of the leaves in onesection with a relatively low heat and air fiow and the drying of theleaves in the other section with a relatively high heat and air flow.

15. A tobacco curing barn comprising a fixed housing section defining atleast two pairs of cooperating vertically spaced inlets and outlets,heating means in said fixed housing section between said inlets andoutlets, means in said fixed housing section for creating an aircirculation from said inlets to said outlets in heat exchange relationto said heating means, means in said fixed housing section forseparately controlling the flow of heated air through each pair ofcooperating inlets and outlets,

at least two elongated housing sections extending horizontally outwardlyfrom said fixed housing section, each of said elongated housing sectionsincluding a pair of spaced a batch of leaves disposed with their fiatsides in substantially parallel vertical relation and spaced horizontalprong means in piercing relation to the leaves in a direc tionperpendicular to the fiat surfaces thereof so as to provide interiorsupport for the leaves while permitting vertical flow of air between theleaves within the confining means, the upper surfaces of said leavesbeing adapted for defining with said roof an upper duct permittinghorizontal flow of air therethrough which is closed at one end, thelower surfaces of said leaves defining with the floor a lower ductclosed at one end, the open end of the upper and lower ducts of eachelongated housing section communicating with one pair of said spacedinlets and outlets whereby the circulation of heated air through eachhousing section is independent of the circulation of heated air throughthe other housing section so as to permit the simultaneous yellowing ofthe leavesin one a 17 drying of the leaves in the other section withrelatively high heat and air flow.

16. In a tobacco curing barn, the combination comprising a barn sectionincluding a bottom floor, a roof, walls extending between said bottomfloor and roof-enclosing the same, an upper intermediate floor structurebetween said walls defining with said roof an upper air chamber, a lowerintermediate floor structure between said walls defining with saidbottom floor a lower air chamber, said intermediate floor structureshaving openings therein, a housing .Wlllhlfi said walls between saidintermediate floor structures, said housing having upper and lowerEopenings communicating respectively with the openings in said upper andlower intermediate floor sections, fan means in said housing having theoutput side thereof communicating with the lower opening in saidhousing, burner means between the upper opening in said housing and theinput side of said fan means, means for controllably communicating asupply of combustion air to said burner means, said walls havingopenings therein communicating with said upper and lower air chambers,and damper means for controlling the flow of air through the openingcommunicating with said lower chamber.

17. The combination as defined in claim 16 including a second barnsection extending horizontally outwardly from said first mentioned barnsection for receiving and supporting in the central portion thereof aplurality of tobacco leaves, said second housing section defining ductspaces above and below the tobacco leaves supported therein, said ductspaces being communicated respectively with the wall openingscommunicating with said air chambers.

18. The combination as defined in claim 16 including a third barnsection extending horizontally outwardly from said first mentioned barnsection for receiving and supporting in the central portion thereof asecond plurality of tobacco leaves, said third housing section definingduct spaces above and below the tobacco leaves supported therein, theduct spaces of said third housing section being communicatedrespectively with said air chambers, and second damper means forcontrolling the communication of said third housing section duct spaceswith said air chambers separate from the control of the communication ofthe second housing section duct spaces therewith.

19. The combination as defined in claim 16 wherein said second housingsection includes a plurality of. units mounted in end-to-end relation,each of said units including spaced vertical imperforate side wallshaving spaced tobacco leaf piercing and supporting prong means extendinghorizontally therebetween.

20. The combination as defined in claim 19 wherein said prong means isconnected directly to said side walls.

21. The combination as defined in claim 19 wherein said prong means isconnected directly to a plurality of peripheral rack frames, said sidewalls having parallel rail means thereon supporting said rack frames.

22. The combination as defined in claim 16 wherein said second housingsection includes a plurality of housing section units mounted inend-to-end relation, each unit being open at its ends and includingspaced imperforate side walls and an irnperforate roof extending betweenthe upper portion of said side walls, said side walls having horizontalrail means thereon for supporting a plurality of tobacco supportingracks therebetween.

23. An air heating and circulating system for curing tobacco supportedin bulk form of substantially uniform density in a plurality of racks ofthe type each of which includes relatively movable sections whichtogether provide means for horizontally peripherally confining a batchof leaves with their flat surfaces disposed generally vertically andwith a substantial portion of their fiat surfaces generally parallel andspaced horizontal prong means extending within the peripheral confiningmeans in piercing relation to the leaves in a direction generallyperpendicular to the parallel flat surfaces thereof so as to provideinl8 terior support for the leaves while permitting vertical flow of airbetween the leaves within the confining means, said system comprising:means defining a duct communicating with the lower surfaces of theleaves; means defining a duct communicating with the upper surfaces ofthe leaves; housing means between said ducts including an inletcommunicating with one of said ducts and an outlet communicating withthe other of said ducts; a burner casing withinsaid housing means havinga burner assembly therein, said burner casing having an air inletcommunieating the interior thereof with the atmopshere exterior of saidhousing means to permit fresh air within said casing to supportcombustion, said burner casing having an outlet communicating theinterior thereof with the interior of the housing means to permit theproducts of combustion to pass into said housing means; fan meansdisposed within said housing means with the pressure side thereofcommunicating with said housing means outlet and the suc-' tion sidethereof communicating with said burner casing outlet and said housingmeans inlet to thereby establish an air flow circuit in which the airfrom the fan means passes through said housing means outlet, throughsaid other duct, vertically through said tobacco leaves, through saidone duct, through said housing means inlet, past said burner casing andthen back to said fan means; means for introducing a controlled amountof fresh air into the circuit on the suction side of said fan means; andmeans for discharging from said one duct to the atmosphere air in thecircuit.

24. An air heating and circulating system as defined in claim 23 whereinsaid last-mentioned means comprises a louvre assembly movable into anopen position in response to a predetermined differential presurebetween the adjacent air in the circuit and atmospheric air to permitdischarge of the air in the circuit and movable into a closed positionin response to a differential pressure below said predetermineddiiferential 'pressure to prevent passage of atmospheric air into saidone duct.

25. An air heating and circulating system as defined in claim 23including means defining a separate air flow circuit between said ductsand through said leaves, and means for alternately communicating saidhousing means between said ducts and said separate circuit definingmeans between said ducts.

' 26. An air heating and circulating system as defined in claim 23wherein said duct communicating with the upper surfaces of said leavesconstitutes said one duct and communicates with said housing meansinlet.

27. An air heating and circulating system for curing tobacco suportedin'bulk form of substantially uniform density in a plurality of racks ofthe type each of which includes relatively movable sections whichtogether provide means for horizontally peripherally confining a batchof leaves with their flat surfaces disposed generally vertically andwith a substantial portion of their flat surfaces generally parallel andspaced horizontal prong means extending within the peripheral confiningmeans in piercing relation to the leaves in a direction generallyperpendicular to the parallel flat surfaces thereof so as to provideinterior support for the leaves while permitting vertical flow of airbetween the leaves within the confining means, said system comprising:means defining a duct communicating with the lower surfaces of theleaves; means defining a duct communicating with the upper surfaces ofthe leaves; first means communicable between said ducts for establishinga yellowing circuit of heated air flow through one of said ducts, theleaves and then the other duct having a relatively slow fiow and arelatively low temperature, second means communicable between said ductsfor establishing a drying circuit of heated air flow through one of saidducts, the leaves and the other of said ducts having a relatively fastflow and a relatively high temperature and means for alternatelycommunicating said first and second means between said ducts.

28. A tobacco curing barn comprising a plurality of vertical wallsdefining a vertically confined space for receiving tobacco leaves, meansextending between said walls for supporting a multiplicity of tobaccoleaves in bulk form therebetween substantially throughout the horizontalextent of said space with the flat surfaces of said leaves extendinggenerally vertically and a substantial portion thereof parallel so as topermit vertical air flow therethrough, means defining a ductcommunicating with the lower surfaces of the leaves, means defining aduct communicating with the upper surfaces of the leaves, housing meansbetween said ducts including an inlet communicating with one of saidducts and an outlet communicating with the other of said ducts, a burnercasing within said housing means having a burner assembly therein, saidburner casing having an air inlet communicating the interior thereofwith the atmospheric exterior of said housing means to permit fresh airto enter said casing so as to support combustion therein, said burnercasing having an outlet communicating the interior thereof with theinterior of said housing means to permit the products of combustionwithin said burner casing to pass into said housing means, fan meansdisposed within said housing means for establishing an air flow circuitin which air passes through said housing means outlet, through saidduct, vertically through said tobacco leaves, through said housing meansinlet, past said burner casing and then back through said housing meansoutlet, means for introducing a controlled amount of fresh air into thecircuit on the suction side of said fan means, and means for dischargingfrom said one duct to the atmosphere air in the circuit.

29. A tobacco curing barn as defined in claim 28 wherein said ductcommunicating with the upper surfaces of said leaves constitutes saidone duct and communicates with said housing means inlet at one endthereof and wherein said means for discharging air in the circuitcomprises an opening in the opposite end of said one duct defining meansand means for controlling the flow of air through said opening.

30. A tobacco curing barn comprising a pair of horizontally spacedvertical walls, horizontal rail means secured to said walls forreceiving and supporting in sideby-side abutting relation the ends of apluality of racks of the type each of which includes relatively movablesections which together provide means for horizontally peripherallyconfining a batch of leaves with their flat surfaces disposed generallyvertically and with a substan-- surfaces thereof so as to provideinterior support for the leaves while permitting vertical flow of airbetween the leaves within the confining means, means extending betweenthe ends of said vertical walls for engaging the adjacent sides of theoutermost racks of said plurality of racks so as to confine passage ofair between the leaves supported in said racks, means defining a ductcommunicating with the lower surface of the leaves, means defining aduct communicating with the upper surfaces of the leaves, housing meansbetween said ducts including an inlet communicating with one of saidducts and an outlet communicating with the other of said ducts, a burnercasing within said housing means having a burner assembly therein, saidburner casing having an air inlet communicating the interior thereofwith the atmospheric exterior of said housing means to permit fresh airto enter said casing so as to support combustion therein, said burnercasing having an outlet communicating the interior thereof with theinterior of said housing means to permit the products of combustionwithin said burner casing to pass into said housing means, fan meansdisposed within said housing means for establishing an air flow circuitin which air passes through said housing means outlet, through saidduct, vertically through said tobacco leaves, through said housing meansinlet, past said burner casing and then back through said housing meansoutlet, means for introducing a controlled amount of fresh air into thecircuit on the suction side of said fan means, and

means for discharging from said one duct to the atmosphere air in thecircuit.

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3. A DEVICE FOR SUPPORTING DEFOLIATED TOBACCO LEAVES IN BULK FORM FORTRANSPORTATION AND CURING COMPRISING A PAIR OF UPRIGHT IMPERFORATE WALLSAND AN IMPERFORATE ROOF EXTENDING BETWEEN THE UPPER PORTION OF SAIDWALLS, MEANS EXTENDING BETWEEN SAID WALLS FOR SUPPORTING A MULTIPLICITYOF TOBACCO LEAVES IN BULK FORM THEREBETWEEN SUBSTANTIALLY THROUGHOUT THELONGITUDINAL EXTENT THEREOF WITH THE FLAT SURFACES OF SAID LEAVESEXTENDING VERTICALLY AND WITH A SUBSTANTIAL PORTION OF THE FLAT SURFACESPARALLEL SO AS TO PERMIT VERTICAL AIR FLOW THERETHROUGH, THE UPPERSURFACES OF SAID LEAVES BEING ADAPTED FOR DEFINING WITH SAID ROOF ANOPEN ENDED DUCT PERMITTING HORIZONTAL FLOW OF AIR THERETHROUGH, SAIDWALLS AND ROOF HAVING MEANS ON EACH OF THE ENDS THEREOF FORSUBSTANTIALLY SEALINGLY ABUTTING THE OPPOSITE END OF A SIMILAR DEVICE,SAID WALLS COMPRISING A PLURALITY OF RECTANGULAR WALL SECTIONS SECUREDTOGETHER IN VERTICALLY STACKED AND END-TO-END RELATION, SAID TOBACCOLEAF SUPPORTING MEANS COMPRISING SPACED HORIZONTALLY EXTENDING PRONGMEANS DIRECTLY CONNECTED BETWEEN EACH PAIR OF SPACED CORRESPONDING WALLSECTIONS.